U.S. patent application number 12/878647 was filed with the patent office on 2011-12-22 for exhaust gas treatment system including a thermoelectric generator.
Invention is credited to Monika Backhaus-Ricoult, Peng Chen, Mark J. Soulliere.
Application Number | 20110311421 12/878647 |
Document ID | / |
Family ID | 44543751 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110311421 |
Kind Code |
A1 |
Backhaus-Ricoult; Monika ;
et al. |
December 22, 2011 |
EXHAUST GAS TREATMENT SYSTEM INCLUDING A THERMOELECTRIC
GENERATOR
Abstract
An after-treatment device for an automotive engine includes a
substrate having a thermoelectric generation element disposed in an
interior volume thereof. The substrate has a first end, a second
end, and an outermost lateral dimension that defines an interior
volume, and is configured to flow engine exhaust gas from the first
end to the second end such that the flowing exhaust gas is in
thermal contact with the thermoelectric generation element.
Inventors: |
Backhaus-Ricoult; Monika;
(Horseheads, NY) ; Chen; Peng; (Painted Post,
NY) ; Soulliere; Mark J.; (Corning, NY) |
Family ID: |
44543751 |
Appl. No.: |
12/878647 |
Filed: |
September 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61356870 |
Jun 21, 2010 |
|
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|
Current U.S.
Class: |
423/213.2 ;
422/173; 422/177 |
Current CPC
Class: |
Y02T 10/16 20130101;
B01D 53/9477 20130101; F01N 13/00 20130101; H01L 35/32 20130101;
Y02T 10/12 20130101; F01N 5/02 20130101; F01N 2240/04 20130101;
B01D 53/9495 20130101; F01N 2260/02 20130101; F01N 2330/06
20130101; B01D 2257/406 20130101; F01N 5/025 20130101 |
Class at
Publication: |
423/213.2 ;
422/177; 422/173 |
International
Class: |
B01D 53/94 20060101
B01D053/94; F01N 3/24 20060101 F01N003/24; B01D 53/34 20060101
B01D053/34 |
Claims
1. An exhaust gas after-treatment device comprising: a substrate
having a first end, a second end, and an outermost lateral
dimension defining an interior volume, wherein the substrate is
configured to flow exhaust gas through the interior volume from the
first end to the second end; and at least one thermoelectric
generation element disposed at least partially within the interior
volume.
2. The device according to claim 1, wherein the substrate comprises
a catalytic substrate.
3. The device according to claim 1, wherein the substrate comprises
a particulate filter substrate.
4. The device according to claim 1, wherein the substrate comprises
a honeycomb structure.
5. The device according to claim 1, wherein the substrate comprises
a metal or a ceramic material selected from the group consisting of
cordierite, silicon carbide, silicon nitride, aluminum titanate,
eucryptite, mullite, alumina, calcium aluminate, zirconium
phosphate, and spodumene.
6. The device according to claim 1, wherein the at least one
thermoelectric generation element is disposed within at least one
cavity formed within the substrate.
7. The device according to claim 1, wherein the at least one
thermoelectric generation element is in direct physical contact
with the substrate.
8. The device according to claim 1, wherein the at least one
thermoelectric generation element is in thermal contact with the
substrate via a thermal transfer medium
9. The device according to claim 1, further comprising a housing
that contains the substrate, and the thermoelectric generation
element is disposed entirely within the housing.
10. The device according to claim 1, further comprising an
integrated cooling circuit in thermal contact with the at least one
thermoelectric generation element.
11. The device according to claim 1, wherein the at least one
thermoelectric generation element is configured to cool the
substrate.
12. The device according to claim 1, wherein the at least one
thermoelectric generation element is configurable to cool or heat
the substrate.
13. The device according to claim 1, further comprising at least
one temperature sensor configured to measure a temperature of the
interior volume.
14. The device according to claim 1, wherein the at least one
thermoelectric generation element comprises a plurality of p-type
components and a plurality of n-type components.
15. The device according to claim 14, wherein the p-type components
and the n-type components are incorporated in a thermoelectric
generator.
16. The device according to claim 14, wherein the p-type components
and the n-type components are arranged in an alternating
checkerboard pattern.
17. The device according to claim 14, wherein the p-type components
and the n-type components comprise alternating p-type and n-type
disks.
18. The device according to claim 14, wherein the p-type components
and the n-type components comprise alternating p-type and n-type
fins.
19. The device according to claim 1, further comprising at least
one thermoelectric generation element disposed outside of the
interior volume.
20. The device according to claim 1, wherein the substrate
comprises a substrate assembly formed from two or more substrate
components.
21. A method for treating exhaust gas, the method comprising:
flowing exhaust gas through an interior volume of a substrate
having a first end, a second end, and an outermost lateral
dimension defining the interior volume; and exchanging heat between
the flowing exhaust gas and at least one thermoelectric generation
element disposed at least partially within the interior volume.
22. The method according to claim 21, further comprising reacting
the exhaust gas with a catalyst during the flowing through the
interior volume.
23. The method according to claim 21, further comprising filtering
the exhaust gas during the flowing through the interior volume.
24. The method according to claim 21, further comprising flowing a
coolant through a cooling circuit in thermal communication with the
at least one thermoelectric generation element.
25. The method according to claim 21, wherein the at least one
thermoelectric generation element comprises a plurality of
thermoelectric generation elements coupled to form a thermoelectric
generator and wherein the method further comprises generating
electricity via the thermoelectric generator.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/356,870, filed Jun. 21, 2010, which is
incorporated by reference herein in its entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to exhaust gas
treatment systems, and particularly to catalytic converter and
particulate filter systems that are integrated with a
thermoelectric generator.
BACKGROUND
[0003] Rising fuel prices and government mandates are driving light
and heavy duty vehicle makers to use technologies that reduce both
fuel consumption and emissions. It is estimated that only about 33%
of the energy from fuel combustion in diesel engines is captured
for vehicle operation, while only about 25% of the combustion
energy in gasoline engines is used to power the drive train and
accessories. In current engine designs, a large fraction of the
combustion energy is lost as waste heat. One approach to fuel
savings involves recycling waste engine heat, which can be
converted into motive or electrical power within the motor
vehicle.
[0004] One method of waste heat recovery is thermoelectric (TE)
generation, whereby direct current (DC) electrical power can be
derived from a TE generation element (e.g., an n-type
semi-conductor plus a p-type semi-conductor) that is exposed to a
thermal gradient. A series connection of TE generation elements
forms a TE generation module. Several TE generation modules can be
connected in a combination of series and parallel configurations to
form a TE generator (TEG). An illustration of an exemplary
electrical connection incorporating a TEG is shown in FIG. 1. As
illustrated in FIG. 1, a plurality of TE generation modules 10 form
a TEG 11, which is electrically connected, for example, to a
vehicle's electrical bus 12 and energy storage system (e.g.,
battery) 13. The current flowing through the connection is
depicted, for example, by an arrow and reference label I. Due to
the possibility of fluctuations in the current and the voltage of
the TEG 11, a DC/DC converter 14 can be used to maintain a line
voltage within a range that is compatible with a vehicle's
electrical system.
[0005] To properly operate, a TEG requires a heat source (i.e. a
higher temperature) and a heat sink (i.e., a lower temperature).
The temperature gradient created induces a flux of electrical
carriers across the TE generation elements. For motor vehicles, the
heat source is generally the heat available within the exhaust gas,
and the heat sink is generally the coolant circulating within the
radiator or an independent cooler system. TEGs have, therefore,
been proposed at various locations in a vehicle's exhaust system.
Accessible sites may include, for example, the exhaust tailpipe
and, particularly for diesel engines, the exhaust gas recirculation
(EGR) loop. TEG prototypes have been built, for example, with
Bi/Pb-telluride and mounted on a vehicle's tailpipe. Such
telluride-based modules have exhibited heat to electrical power
conversion efficiencies up to about 10%. EGR loop TEGs are also
under development, focusing mainly on skutterudite materials, which
for this application may have efficiencies of about 3-10% dependent
on the recycled fraction.
[0006] There are, however, various factors to consider when
designing and implementing a TEG within an exhaust system. Such
factors can include the available hot temperatures, the heat flow,
the proximity of the heat source and sink to the TEG, the footprint
of the TEG in view of the limited space available within an engine
compartment or on the underside of a vehicle chassis, and the
desire to minimize the mass added to the vehicle. A TEG added to
the exhaust gas stream may further undesirably increase the
pressure drop or back-pressure on the engine, thereby increasing
fuel consumption. Consequently, various challenges may arise in
using conventional TEGs in light of space requirements, and the
resulting increase in mass and back-pressure.
[0007] It may therefore be desirable to integrate a TEG within
existing exhaust gas after-treatment devices, such as, for example,
catalytic substrates and/or particulate filters, to profit from
high available temperatures (e.g., compared with tailpipe
locations), high heat flux, reduce the number of components to be
carried by the vehicle, and avoid additional back-pressure on the
engine. Furthermore, after-treatment device operation windows are
generally limited by the high temperatures (e.g., catalytic
conversion and filter regeneration operation windows), which may
lead to temperature gradients within the devices and
thermo-mechanical durability-limiting associated stresses.
Therefore, it may also be desirable to integrate a TEG within
existing exhaust gas after-treatment devices to widen the operation
windows of the after-treatment devices, while also maximizing waste
heat recovery in the vehicle.
SUMMARY
[0008] In view of the foregoing, economical, efficient and
minimally invasive waste heat recovery systems are desirable. The
disclosure may solve one or more of the above-mentioned problems
and/or may demonstrate one or more of the above-mentioned needs.
Other features and/or advantages may become apparent from the
description that follows.
[0009] In accordance with various exemplary embodiments of the
present disclosure, an exhaust gas after-treatment device may
comprise a substrate having a first end, a second end, and an
outermost lateral dimension defining an interior volume, wherein
the substrate is configured to flow exhaust gas through the
interior volume from the first end to the second end. The
after-treatment device may further comprise at least one
thermoelectric generation element disposed at least partially
within the interior volume.
[0010] In accordance with various additional exemplary embodiments
of the present disclosure, a method for treating exhaust gas may
comprise flowing exhaust gas through an interior volume of a
substrate having a first end, a second end, and an outermost
lateral dimension defining the interior volume. The method may
further comprise exchanging heat between the flowing exhaust gas
and at least one thermoelectric generation element disposed at
least partially within the interior volume.
[0011] Additional features and advantages of the disclosure will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from that
description or recognized by practicing the present teachings as
described herein, including the detailed description which follows,
the claims, as well as the appended drawings.
[0012] It is to be understood that both the foregoing general
description and the following detailed description present
exemplary embodiments of the disclosure, and are intended to
provide an overview or framework for understanding the nature and
character of the present disclosure as it is claimed. The
accompanying drawings are included to provide a further
understanding of the disclosure, and are incorporated into and
constitute a part of this specification. The drawings illustrate
various embodiments of the disclosure and together with the
description serve to explain the principles and operations of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic of an exemplary electrical connection
for a TEG within a motor vehicle;
[0014] FIG. 2 illustrates possible TEG locations relative to
after-treatment devices of a gasoline engine;
[0015] FIG. 3 illustrates possible TEG locations relative to
after-treatment devices of a diesel engine;
[0016] FIGS. 4a and 4b show the interrelationship among various TE
material properties;
[0017] FIG. 5a is a schematic of a TE generation element;
[0018] FIG. 5b is a plot of thermoelectric efficiency versus the
Figure of Merit (ZT) for two different hot side temperatures and
one fixed cold side temperature;
[0019] FIG. 6 is a schematic illustration of an exemplary TE
generation module;
[0020] FIG. 7 is a schematic showing the temperature distribution
(T) across the transverse direction (R) of a substrate;
[0021] FIG. 8a is a schematic illustration of an after-treatment
device having a TEG disposed within a central core;
[0022] FIGS. 8b and 8c illustrate exemplary embodiments of TE
generation element patterns;
[0023] FIG. 9 illustrates an exemplary outermost lateral dimension
of a substrate;
[0024] FIG. 10 is a schematic of an after-treatment device having a
TEG with a cooling circuit disposed along a central core of the
substrate;
[0025] FIG. 11a is a schematic illustrating a monolithic substrate
having a cavity formed by drilling;
[0026] FIG. 11b is a schematic illustrating a monolithic substrate
having a cavity formed in situ by extrusion;
[0027] FIG. 11c is a schematic illustrating a monolithic substrate
having a cavity formed using multiple substrate portions;
[0028] FIG. 12 shows an after-treatment device having disc-shaped
TEGs and a common cooling channel placed within a circular
cavity;
[0029] FIG. 13 shows an after-treatment device having plural TEGs
and a common cooling channel placed within a circular cavity;
[0030] FIG. 14 shows an after-treatment device having plural TEGs
with respective cooling channels placed within a circular
cavity;
[0031] FIG. 15 shows an after-treatment device having plural TEGs
and a common cooling channel placed within a triangular cavity;
[0032] FIG. 16 shows an after-treatment device having plural TEGs
and a common cooling channel placed within a square cavity;
[0033] FIG. 17 shows an after-treatment device having plural TEGs
and a common cooling channel placed within a cross-shaped
cavity;
[0034] FIG. 18 shows an after-treatment device having a plurality
of circular cavities with a TEG placed in each cavity;
[0035] FIGS. 19a and 19b are schematics illustrating electrical
interconnections among a plurality of TE generation elements;
[0036] FIG. 20 is a schematic illustrating a fitting configuration
for an after-treatment device having integrated TEGs;
[0037] FIG. 21 shows an after-treatment device having TEGs disposed
within cavities at the end of peripheral slots;
[0038] FIG. 22 shows an after-treatment device having plural TEGs
and cooling channels disposed within cavities at the end of
peripheral slots;
[0039] FIG. 23 is a schematic illustrating a fitting configuration
for an after-treatment device having one peripheral slot;
[0040] FIG. 24 shows an after-treatment device having TEGs disposed
within a cavity and located around the periphery of the
after-treatment device;
[0041] FIG. 25 shows an after-treatment device having TEGs disposed
partially within the interior volume of a substrate;
[0042] FIG. 26 shows results obtained from numerical modeling of
thermal energy draw (W) as a function of vehicle speed (km/hr) for
a first substrate sample;
[0043] FIG. 27 shows results obtained from numerical modeling of
thermal energy draw (W) as a function of vehicle speed (km/hr) for
a second substrate sample;
[0044] FIG. 28 shows results obtained from numerical modeling of
thermal energy drawn flux (W/m.sup.2) as a function of vehicle
speed (km/hr) for the substrate samples of FIGS. 26 and 27; and
[0045] FIG. 29 shows results obtained from numerical modeling of
thermal energy draw (W) as a function of inner mat conductivity
(W/m-K) for the substrate sample of FIG. 27.
DETAILED DESCRIPTION
[0046] According to an exemplary embodiment, an exhaust gas
after-treatment system having a thermoelectric generator (TEG)
disposed within an after-treatment substrate is disclosed. In
accordance with the present disclosure, the substrate, such as, for
example, a catalytic substrate or a particulate filter substrate,
is adapted to flow exhaust gas from a first end of the substrate to
a second end of the substrate within an outermost lateral dimension
that defines an interior volume of the substrate. Disposed at least
partially within the interior volume is at least one thermoelectric
generation element.
[0047] By incorporating a thermoelectric (TE) generation element
within an interior volume of the substrate, higher hot-side
temperatures and hence greater conversion efficiencies may be
achieved. In addition, placement of the TE generation element
within the interior volume may advantageously promote
homogenization of the overall substrate temperature during its
operation, particularly with low thermal conductivity substrates,
thereby also significantly widening the substrate's operation
window.
[0048] In a gasoline engine, for example, exhaust gas can pass
through one or more three-way catalyst (TWC) substrates. As
illustrated schematically in FIG. 2, typical gasoline
after-treatment systems include a TWC substrate 20 that is
close-coupled to an engine 21, along with another underbody TWC
substrate 20 further downstream. As shown in FIG. 2, in various
exemplary embodiments, a gasoline particulate filter (GPF)
substrate 22 may also be provided. As those of ordinary skill in
the art would understand, during operation of the engine 21, air
enters via an air intake 23, is compressed by a turbocharger 24,
cooled by an inter-cooler 25, and passes through intake valves 26
into the engine's 21 cylinders. After fuel is added and ignited,
exhaust gas emerges from exhaust valves 27, is combined in an
exhaust manifold 28, spins the turbocharger 24 (if present), and
passes through the TWCs 20 and GPF 22.
[0049] The thermal mass of the TWC substrates 20 and/or the GPF
substrate 22 allows for heat storage (i.e., the heat source) from
exhaust gas passing through the after-treatment system, and engine
coolant may be, for example, routed through the after-treatment
system from a radiator 29 via a coolant pipe 30 to act as the heat
sink. Accordingly, in the gasoline engine, as illustrated in FIG.
2, there are various potential sites (PS) for integrating a TEG
within an after-treatment substrate.
[0050] During operation of a diesel engine 31, as shown
schematically in FIG. 3, exhaust gas that emerges from the exhaust
manifold 28 has a second possible return path to the intake valves
26, i.e., via an exhaust gas recirculation loop (EGR) 32, which
passes through an EGR cooler 36. As with the gasoline engine 21,
however, the remaining exhaust gas passes through a series of
after-treatment elements. Catalyst substrates may include, for
example, as shown in FIG. 3, a diesel oxidation catalyst (DOC)
substrate 33, a selective catalytic reduction (SCR) catalyst
substrate 34, and an ammonia slip catalyst substrate 35. In various
exemplary embodiments, a diesel vehicle may also substitute a lean
NOx trap (LNT) for the SCR and ammonia slip catalyst substrates. As
those of ordinary skill in the art would understand, catalyst
substrates are often composed of a cellular ceramic or metal
substrate, which is coated with the catalytic material.
[0051] In various exemplary embodiments, in addition to catalyst
substrates, as shown in FIG. 3, the diesel engine 31 may also
include a diesel particulate filter (DPF) substrate 37. As those of
ordinary skill in the art would further understand, the DPF
substrate 37 can be made, for example, using various porous
cellular ceramic substrates whose ends are plugged in a
checkerboard fashion, or by using a partial flow filter made, for
example, of corrugated metal sheets.
[0052] As above, the thermal mass of the catalytic substrates 33,
34 and 35 and/or the DPF substrate 37 may therefore act as heat
storage (i.e., the heat source) for exhaust gas passing through the
after-treatment system. And engine coolant may be, for example,
routed through the after-treatment system from a radiator 29 via a
coolant pipe 30 to act as the heat sink. Accordingly, in the diesel
engine, as illustrated in FIG. 3, there are various potential sites
(PS) for integrating a TEG within an after-treatment substrate.
[0053] As used herein, a "substrate" or an "after-treatment
substrate" includes catalytic substrates and particulate filter
substrates that are intended to remove pollutants from engine
exhaust gas. Substrates may include, for example, a porous body
made from various metal and ceramic materials, including, but not
limited to, cordierite, silicon carbide (SiC), silicon nitride,
aluminum titanate (AT), eucryptite, mullite, calcium aluminate,
zirconium phosphate and spodumene. A "catalyst substrate" may
include, for example, a porous body, such as a TWC, DOC or SCR,
which is infiltrated with a catalyst that assists a chemical
reaction to reduce or eliminate the concentration of various
pollutants within the exhaust gas (e.g., monoxide, nitrogen oxides,
sulfur oxide, and hydrocarbons). A "particulate filter substrate"
may include, for example, a porous body, such as a GPF or DPF
substrate, which traps and therefore reduces particulate matter
within the exhaust stream (e.g., soot and ash).
[0054] The substrates of the present disclosure can have any shape
or geometry suitable for a particular application, as well as a
variety of configurations and designs, including, but not limited
to, a flow-through structure, a wall-flow structure, or any
combination thereof (e.g., a partial-flow structure). Exemplary
flow-through structures include, for example, any structure
comprising channels or porous networks or other passages that are
open at both ends and permit the flow of exhaust gas through the
passages from one end to an opposite end. Exemplary wall-flow
structures include, for example, any structure comprising channels
or porous networks or other passages with individual passages open
and plugged at opposite ends of the structure, thereby enhancing
gas flow through the channel walls as the exhaust gas flows from
one end to the other. Exemplary partial-flow structures include,
for example, any structure that is partially flow-through and
partially wall-flow. In various exemplary embodiments, the
substrates, including those substrate structures described above,
may be monolithic structures. Various exemplary embodiments of the
present teachings, contemplate utilizing the cellular geometry of a
honeycomb configuration due to its high surface area per unit
volume for deposition of soot and ash. Those having ordinary skill
in the art will understand that the cross-section of the cells of a
honeycomb structure may have virtually any shape and are not
limited to square or hexagonal. Similarly, a honeycomb structure
may be configured as either a flow-through structure, a wall-flow
structure, or a partial-flow structure.
[0055] To recover electricity from waste heat, such as exhaust heat
passing through an after-treatment system as shown and described
above with reference to FIGS. 2 and 3, the present disclosure
contemplates integrating various high-temperature TE materials
within after-treatment substrates. As those of ordinary skill in
the art would understand, suitable TE materials generally produce a
large thermopower when exposed to a temperature gradient. Suitable
materials, for example, usually exhibit a strong dependency of
their carrier concentration on temperature, have high carrier
mobility, and low thermal conductivity. As those of ordinary skill
would further understand, suitable materials, which may recover a
large fraction of heat energy, generally have a large Figure of
Merit ZT, defined as ZT=T*S.sup.2*(.sigma./.kappa.), wherein T is
temperature (in Kelvin), S is the Seebeck coefficient or
thermopower (in V/m), .sigma. is the electric conductivity (in
Siemens/m), and .kappa. is the thermal conductivity (in W/mK). As
would be also understood, the Seebeck voltage describes the
potential difference that is established across a material exposed
to a temperature gradient; and the Seebeck coefficient is obtained
by extrapolating the Seebeck voltage to a vanishing temperature
gradient. Depending on the majority carrier type in the material,
the Seebeck coefficient can be positive or negative. These
relationships are illustrated in FIGS. 4a and 4b for various
materials (i.e., insulating materials I, semiconductor materials
SC, semimetal or heavily doped semiconductor materials SM, and
metal materials M), showing the relationship of the Seebeck
coefficient (.alpha.) S, Power Factor
(.alpha..sup.2/.rho.=.alpha..sup.2.sigma.) PF, and Conductivity
(.sigma.=1/.rho.) C.
[0056] As illustrated with reference to FIG. 5a, an exemplary TE
generation element (e.g., that comprises interconnected n-type and
p-type semi-conductors) is the building block of a TEG. A TE
generation couple is built, for example, of an assembly of
interconnected p-legs and n-legs composed of p-type and n-type TE
materials (e.g., n-type and p-type semi-conductors). As shown in
FIG. 5a, when the TE generation couple is exposed to a heat source
H and a heat sink C, which creates a temperature gradient .DELTA.T
across the couple, a current I flows clockwise around the circuit.
A plot of the efficiency of converting heat into electricity as a
function of the Figure of Merit ZT is illustrated in FIG. 5b. As
shown in FIG. 5b, for a material having a ZT value of about 1.5,
the conversion efficiency is about 10% for a temperature gradient
of about 200K (i.e., T.sub.hot=500K-T.sub.cold=300K) and about 20%
for a temperature gradient of about 550K (i.e.,
T.sub.hot=850K-T.sub.cold=300K).
[0057] As those of ordinary skill in the art would also understand,
various shapes and arrangements of TE legs have been proposed for
integrating TE materials and components into a TEG. For exemplary
purposes only, one exemplary TE generation module is illustrated in
FIG. 6. As shown in FIG. 6, a TE module 60 may be built between
plates 63 and 65, respectively located on a hot side A and cold
side R of the module 60 (e.g., as respectively shown by arrows A
and R, heat is absorbed through the top surface of plate 63 and
rejected through the bottom surface of plate 65). Plates 63 and 65
thereby act respectively as the heat source and heat sink for the
module 60. Alternating p-legs and n-legs 61 are interconnected in
series by metal interconnects 62 on both the hot and cold sides of
the module 60, so that the total voltage of the module 60 is made
available at end leads 64. As those of ordinary skill in the art
would understand, instead of the simple plates 63 and 65 shown in
FIG. 6, a TEG will generally contain efficient heat exchangers that
guarantee efficient heat exchange between the hot and cold sources.
Those of ordinary skill in art would understand, however, that
various TEG designs and/or configurations are considered by the
present disclosure and claims.
[0058] As above, in various exemplary embodiments, a substrate
(e.g., a catalytic substrate or particulate filter substrate) may
comprise a variety of materials, including materials having a
relatively high thermal conductivity and/or materials having a
relatively low thermal conductivity. In various embodiments, for
example, a substrate may comprise a metallic material having a
thermal conductivity in the range of about 20 W/mK to about 25
W/mK. Whereas in various additional embodiments, a substrate may
comprise a ceramic material having a thermal conductivity in the
range of about 0.5 W/mK to about 20 W/mK. In various embodiments,
the substrate may also include a honeycomb structure, wherein the
overall thermal conductivity can be further reduced by increasing
the porosity and decreasing the wall thickness.
[0059] As would be understood by those of ordinary skill in the
art, the temperature distribution within a substrate (e.g., a
catalytic substrate or particulate filter substrate) is a function
of a number of parameters. For catalytic substrates, the substrate
temperature (and temperature profile) may be a function of the type
of engine, the type of fuel, the configuration of the
after-treatment system, and various other factors. As visualized in
the temperature distribution profile shown in FIG. 7 adjacent the
substrate 80, in a gasoline engine, for example, the substrate 80
may be several hundred degrees cooler at the periphery compared to
the core (with T indicating temperature and R indicating transverse
distance in the temperature distribution profile). For efficient
operation of the catalytic substrate, desired operational
parameters include a substantially homogeneous temperature
distribution across the substrate, flow homogeneity, and fast light
off. The transverse (e.g., radial for the substrate configuration
of FIG. 7) temperature gradient depicted in FIG. 7 may therefore
result in a less efficient use of the catalyst in the outer, colder
periphery of the substrate 80 in the case of a catalytic substrate,
or lead to overheating of the catalyst and substrate compared to
the needed operation temperature.
[0060] In an un-catalyzed particulate filter substrate, such as for
example a DPF substrate, where the temperature is typically a
function of the location of the filter within the exhaust system
(i.e., a standard configuration versus a close-coupled
configuration), the average substrate temperature is typically less
than the average catalytic substrate temperature. A DPF substrate,
for example, operates in two principal regimes, a regular operating
regime (i.e., a base temperature for either catalyzed or
un-catalyzed filters) and a regeneration regime. During filter
regeneration, temperatures may peak to considerable values, wherein
a filter's core temperature can be several hundred degrees higher
than the temperature at the periphery, thereby also resulting in a
strong radial temperature gradient. Such temperature gradients make
it difficult for substrates (e.g., catalytic substrates and
particulate filter substrates) to remain within an acceptable
operation window.
[0061] Transverse temperature gradients in both catalytic
substrates and particulate filter substrates may, therefore, limit
the operational window of low thermal conductivity filters. One
approach to decreasing the temperature gradient is to use higher
thermal conductivity materials for the substrate. In accordance
with the present disclosure, the temperature gradient in a
substrate may also be decreased by integrating at least one TE
generation element within the substrate, thereby extending the
substrate's operation window and providing waste heat recovery
within the vehicle.
[0062] As illustrated in FIG. 8a, in accordance with various
exemplary embodiments of the present disclosure, an after-treatment
device 100 may comprise a substrate 106 having a first end 101, a
second end 102, and an outermost lateral dimension 103, defining an
interior volume 104. As explained above, when placed within an
after-treatment system, the substrate 106 is configured to flow
exhaust gas through the interior volume 104 from the first end 101
to the second end 102. In various embodiments, for example, the
substrate is a structure comprising a plurality of channels 115
that permit the flow of exhaust gas through the channels 115 from
the first end 101 to the second end 102. In an exemplary
embodiment, the substrate comprising channels may have a honeycomb
configuration; however, those ordinarily skilled in the art would
recognize that the channels may have a variety of arrangements and
configurations (e.g., cross-sections) without departing from the
scope of the disclosure. For ease of reference only, channels are
not shown in FIGS. 9-18 and 20-25.
[0063] As used herein the term "outermost lateral dimension" refers
to an outer peripheral boundary surface (portions of which can be
imaginary) defined by the largest distance between the center of
the substrate and the skin of the substrate. By way of example, for
a substrate having a circular cross-section, the "outermost lateral
dimension" is defined by the radius of the substrate. Accordingly,
as shown, for example, with reference to FIG. 9, if a substrate 200
is not perfectly circular (i.e., has notches 201 or other
indentations, slots, or openings formed in the peripheral surface),
the outermost lateral dimension 203 is defined by the convex shadow
enveloping the substrate 200 defined by the largest radius r
between the center 202 of the substrate 200 and the skin 204 of the
substrate 200 (including the concave portions 205 introduced by the
notches 201). Thus, in the exemplary embodiment of FIG. 9, portions
of the outermost lateral dimension coincide with the peripheral
surface of the substrate 200 (i.e., surfaces excluding notches) and
other portions include imaginary surface portions (i.e., surfaces
including notches 201).
[0064] As used herein the term "interior volume" refers to the
volume bounded by the outermost later dimension. With reference
again to FIG. 9, the interior volume is the volume defined by the
outermost lateral dimension 203, which includes both the volume of
the substrate 200 and the volume of the notches 201 (defined by the
concave portions 205).
[0065] In accordance with the present disclosure, at least one
thermoelectric (TE) generation element is disposed at least
partially within the interior volume 104. As shown in FIGS. 8b and
8c, a TEG 105 may comprise different patterns of TE generation
elements 109 including, for example, a checkerboard pattern with
alternating n-type and p-type legs (FIG. 8b), a stack of n-type and
p-type disks (FIG. 8c), radially-extending n-type and p-type fins,
or combinations thereof. Those of ordinary skill in the art would
understand, however, that various patterns of TE generation
elements 109 can be used without departing from the present
disclosure or claims. As those of ordinary skill in the art would
understand, the n-legs and p-legs are separated from each other.
Suitable separating layers may be made, for example, from a low
thermal conductivity, low electrical conductivity material, such
as, for example, a ceramic or glass-ceramic foam, coating or
interlayer.
[0066] In various exemplary embodiments, TE generation elements 109
are in direct physical contact with the substrate 106. In various
additional embodiments, the TE generation elements 109 may be in
thermal contact with the substrate 106 via a thermal transfer
medium. As those of ordinary skill in the art would understand, the
thermal transfer medium can be formed from any type of conforming,
thermally conductive substance. The thermal transfer medium may
serve, for example, to conform to the surfaces of the TE generation
elements 109 and the substrate 106 to effectively enhance thermal
transfer from the heat source or cooling source to the TE
generation module. Those of ordinary skill in the art would
understand that suitable thermal transfer materials may comprise
materials having a low electrical conductivity and a high thermal
conductivity, including, for example, metallic foams, nets, and
metal-ceramics.
[0067] As noted previously with respect to FIG. 7, a substrate may
demonstrate a higher temperature in its core than at its periphery.
Such radial transverse thermal gradients may introduce stress
within a substrate and limit its thermo-mechanical durability and
operation window. Accordingly, in various exemplary embodiments,
the temperature gradients across the substrate and hence the
thermally-generated stress can be reduced by locating one or more
TE generation elements or coolant flow in the hottest region of the
substrate, i.e., along the core. This geometry, where the TE
generation elements 109 are proximate the substrate 106 and the
coolant flow runs along a central axis of the substrate 106 via an
integrated cooling circuit 108 in thermal contact with the TE
generation elements 109, is illustrated in FIGS. 8a and 10. As
illustrated in FIG. 10, for example, the substrate 106 may comprise
a central cavity 107 having a volume 70 for the TE generation
elements 109 (e.g., comprising the TEG 105 as shown in FIGS. 8a, 8b
and 8c) with a volume 71 for the integrated cooling circuit 108
(shown in FIG. 8a). In such a configuration, the cooling effect of
the cooling circuit 108 (i.e., the heat sink) limits the maximum
core temperatures and helps to decrease the temperature gradients
across the substrate. Accordingly, the thermo-mechanical
reliability of the substrate is strongly enhanced and its operation
window is enlarged, thereby allowing for higher soot mass in a
filter substrate and/or higher temperature spikes in a catalytic
substrate. In various embodiments, the TE generation elements 109
can, therefore, be configured to cool the substrate 106. In various
embodiments, for example, coolant flow adjacent to the TE
generation elements 109 can be used to control the TEG 105 in
response to the temperature of the substrate 106. For example, in
various embodiments, the after-treatment device 100 may further
comprise at least one temperature sensor that is configured to
measure a temperature of the interior volume 104, and the coolant
flow can be adjusted (increased or decreased) in response to the
measured temperature. In various embodiments, for example, the
coolant flow can be adjusted in response to a regeneration event
associated with a particulate filter substrate. In various
additional embodiments, the coolant flow in the catalytic convertor
can be adjusted to preserve a threshold temperature for the
catalytic activity. As those of ordinary skill in the art would
understand, in various further embodiments, to auto-regulate the
amount of heat pulled from the substrate, a TE material with a
steep, step function in its ZT performance with temperature can
optionally be applied to allow for a threshold response.
[0068] Locating the heat sink (i.e., the integrated cooling circuit
108) at or near the hottest zone of the substrate can also transfer
heat to warm up the engine coolant during cold starts. This can
facilitate faster heating of, for example, the passenger cabin in a
motor vehicle, as well as the engine block and engine oil, which
can reduce engine friction. Accordingly, in various additional
embodiments, the TE generation elements 109 can be configured to
heat the substrate 106.
[0069] As illustrated in FIG. 8a, a cavity 107 (e.g., a conduit
that is open at both ends) may be formed within a central core
(within the interior volume 104) of the substrate 106, and the TEG
105 and the integrated cooling circuit 108 may be disposed within
the cavity 107. Thus, the TEG 105 is positioned between a heat
source (the substrate 106) and a heat sink (the cooling circuit
108). As would be understood by those of ordinary skill in the art,
depending on a particular application and substrate geometry, the
TEG 105 and the integrated cooling circuit 108 may have various
configurations within the cavity 107. Accordingly, in accordance
with the present disclosure, various substrate geometries, TEG
geometries, and exhaust after-treatment system configurations are
disclosed below.
[0070] As would be further understood by those of ordinary skill in
the art, a number of approaches can be used to form the
longitudinal cavity 107 within the substrate 106. In various
embodiments, as illustrated in FIG. 11a, the substrate 106 can be
formed and the cavity 107 can be drilled from a previously-formed
substrate 106. A drilled cavity 107 could, however, leave a
roughened inner surface 120 of the cavity 107. Thus, to improve
thermal contact between the substrate 106 and a TEG, an
electrically insulating thermal transfer medium layer 110 can be
implemented on the inner surface 120 of the drilled cavity 107. As
would be understood by those of ordinary skill, the electrically
insulating layer 110 may be formed by various methods, including,
but not limited to, dip coating, spray coating or direct fitting of
a pre-formed layer.
[0071] In various additional embodiments, as illustrated in FIG.
11b, the cavity 107 can be formed in situ during formation of the
substrate 106, such as via extrusion where the extrusion die is
modified to form the cavity 107 when the substrate 106 is formed.
As with the drilling embodiment of FIG. 11a, an electrically
insulating thermal transfer medium layer 110 may optionally be
formed on an inner surface 120 of the cavity 107.
[0072] As illustrated in FIG. 11c, in various further embodiments,
a substrate assembly 106 having a central cavity 107 can be
fashioned by forming, such as by extrusion for example, two or more
separate substrate components 111 and 112 that when assembled
(e.g., via closing an air gap 113 shown for illustrative purposes
in FIG. 11c) produce the desired form factor.
[0073] A cavity can have any suitable geometry and/or
cross-sectional shape, including circular (as shown in FIGS. 8a,
10, and 11), square, rectangular, oval, etc. FIG. 12, for example,
illustrates a substrate 306 having a circular cavity 307 with a
disc-shaped TEG 305 (see FIG. 8c) disposed therein. The disc-shaped
p-legs and n-legs are separated by an electrically and thermally
insulating layer. An electrically insulating heat transfer layer
310 (i.e., a thermal transfer medium) separates the TEG 305 from
the body of the substrate 306. An optional electrically insulating
layer 311 separates the TEG 305 from a cooling medium, such as, for
example, an integrated cooling circuit 308 (i.e., a common cooling
channel) defined by a pipe 312 configured to flow a coolant 313
therethrough. As above, a disc-shaped TEG 305 can be used,
particularly with substrates having circular cavities, to improve
the thermal contact between the TE generation elements (not shown)
and the substrate 306.
[0074] As also illustrated in FIG. 12, cross-hatching is used
throughout the figures for ease of differentiating the various
elements shown. Those of ordinary skill in the art would understand
that the cross-hatching is for delineation purposes only and not
intended to limit the disclosure or claims in any manner.
[0075] A substrate 406 having a central, circular cavity 407
comprising multiple rectangular TEGs 405 is illustrated in FIG. 13.
Within the cavity 407, an electrically insulating heat transfer
layer 410 separates the TEGs 405 from the body of the substrate
406, while an optional electrically insulating layer 411 separates
the TEGs 405 from the cooling medium, such as, for example, an
integrated cooling circuit 408 defined by a rectangular pipe 412
configured to flow a coolant 413 therethrough.
[0076] As illustrated in FIG. 14, in an alternate embodiment, a
substrate 506 having a central, circular cavity 507 may comprise
multiple (4 being depicted in the exemplary embodiment of FIG. 14)
rectangular TEGs 505, each being in thermal contact with a
respective cooling circuit 508 (i.e., cooling channel) defined by a
rectangular pipe 512 configured to flow coolant 513 therethrough.
An electrically insulating heat transfer layer 510 separates each
TEG 505 from the body of the substrate 506, while an optional
electrically insulating layer 511 separates each TEG 505 from a
cooling circuit 508. In the embodiment of FIG. 14, for example,
each TEG 505 is oriented to have improved thermal contact with the
electrically insulating heat transfer layer 510, thereby improving
thermal contact with the substrate 506.
[0077] As shown in FIGS. 15-17, in various exemplary embodiments, a
polygonal cavity having i.sub.element sides, where i.sub.element is
the number of transverse TE generation elements disposed within the
cavity, may be used instead of a circular cavity. Furthermore, in
embodiments having a polygonal cavity, the length of the sides of
the polygon can be equal or unequal. For instance, the length of
the sides of the polygon can be equal if the TEGs themselves all
have the same transverse dimension. If the TEGs, however, have
varying transverse dimensions or if the coefficient of thermal
expansion (CTE) of the substrate is anisotropic (i.e., has
properties that differ in the x and y directions), the cavity
dimensions may be adjusted to allow for longer TEGs in one
preferred dimension.
[0078] FIG. 15, for example, illustrates a substrate 606 having a
triangular cavity 607. As shown in FIG. 15, three TEGs 605 are
fitted into the cavity 607. As above, the TEGs 605 are separated
from the substrate 606 by an electrically insulating heat transfer
layer 610, and are separated from a central cooling circuit 608 by
an optional electrically insulating layer 611. The central cooling
circuit 608 is defined by a triangular pipe 612 configured to flow
coolant 613 therethrough.
[0079] FIG. 16 illustrates a substrate 706 having a square cavity
707. As shown in FIG. 16, four TEGs 705 are fitted into the cavity
707. The TEGs 705 are separated from the substrate 706 by an
electrically insulating heat transfer layer 710, and are separated
from a central cooling circuit 708 by an optional electrically
insulating layer 711. The central cooling circuit 708 is defined by
a square pipe 712 configured to flow coolant 713 therethrough.
[0080] FIG. 17 illustrates a substrate 806 having a cross-shaped
cavity 807. As shown in FIG. 17, twelve TEGs 805 are fitted into
the cavity 807. The TEGs 805 are separated from the substrate 806
by an electrically insulating heat transfer layer 810, and are
separated from a central cooling circuit 808 by an optional
electrically insulating layer 811. The central cooling circuit 808
is defined by a cross-shaped pipe 812 configured to flow coolant
813 therethrough. As would be understood by those of ordinary skill
in the art, such a multi-sided structure can be used to increase
the available contact surface area between the TEGs 805 and the
substrate 806.
[0081] In various additional exemplary embodiments, as illustrated
in FIG. 18 multiple cavities 107 may be formed within the substrate
106. As shown in FIG. 18, for example, three circular cavities 107
may be formed within the substrate 106, each cavity 107 having a
volume 70 for TE generation elements (e.g., comprising TEGS) and a
volume 71 which may contain an integrated cooling circuit. Those of
ordinary skill in the art would understand, however, that the
embodiment of FIG. 18 is exemplary only and that a substrate can
have various numbers and/or configuration of cavities without
departing from the scope of the present disclosure and claims. It
would be appreciated, for example, that when multiple cavities are
used, various cavity shapes are also contemplated, and that a shape
of one cavity may be the same or different from the shape of a
second cavity. Accordingly, in both single cavity and multiple
cavity embodiments, a skilled artisan would be able determine the
appropriate size and position of each cavity. For instance,
cavities may be positioned symmetrically or asymmetrically within a
substrate in order to balance CTE asymmetries. Those of ordinary
skill in the art would understand, however, that in all of the
foregoing embodiments, the TE generation elements and coolant
channels are located within the interior volume of the substrate
(defined by the outermost lateral dimension of the substrate) and
hence interior to a housing or exhaust gas container (i.e., a can)
that may contain the substrate. Those of ordinary skill in the art
would additionally understand that the TE generation elements
and/or coolant channels may extend along the entire length of the
interior volume of the substrate and/or only partially along the
length of the interior volume. Furthermore, multiple TE generation
elements may be placed within the interior volume.
[0082] Schematics of possible electrical interconnections among the
various TE generation elements 309 within an exemplary substrate
306 of FIG. 12 are illustrated in the partial cross-sectional views
of FIGS. 19a and 19b (which show a view of a substrate
cross-section from the center to the outer periphery). As shown, a
TEG 305 may comprise various patterns of alternating TE generation
elements 309. In various embodiments, for example, the TE
generation elements 309 may comprise a plurality of n-type
components 320 and a plurality of p-type components 321. As above,
in various embodiments, the n-type components 320 and the p-type
components 321 are arranged in an alternating checkerboard pattern
(e.g., similar to that shown in FIG. 8b), whereas in various
additional embodiments, the n-type components 320 and the p-type
components 321 comprise alternating p-type and n-type cubes,
hexagons, disks (e.g., similar to that shown in FIG. 8b), fins or
otherwise shaped blocks.
[0083] As shown in FIGS. 19a and 19b, an electrically insulating
heat transfer layer 310 (i.e., a thermal transfer medium) separates
the TE generation elements 309 from the body of the substrate 306,
and an electrically insulating layer 311 separates the TE
generation elements 309 from the cooling medium, such as, for
example, an integrated cooling circuit 308 defined by a pipe 312
configured to flow a coolant 313 therethrough. In various
embodiments, for example, the insulating layers 310 and 311 can be
patterned to also separate current collectors 323 on one or both of
the heat source and heat sink sides. The current flowing through
the current collectors 323 being depicted by the arrow and
reference label I in FIGS. 19a and 19b. An air, gas or vacuum space
322 separates the n-type components 320 from the p-type components
321. As shown in FIG. 19a, in various embodiments, the space 322
may be lined with an electrically insulating material (i.e.,
insulating layers 310 and 311 are contiguous). Alternatively, as
shown in FIG. 19b, in various additional embodiments, the current
collectors 323 may be coated with an electrical insulating material
(i.e., insulating layers 310 and 311 are not contiguous and match
the dimensions of the current collectors 323). As would be
understood by those of ordinary skill in the art, for particulate
filter substrate embodiments, lining spaces 322 with an
electrically insulating material (FIG. 19a) that is also impervious
to particulates, may improve TEG function. Such a configuration,
for example, may prevent conducting particulates contained in the
exhaust gas from gathering immediately adjacent to the TE
generation elements (which could burn during a regeneration event)
and possibly create short-circuits between the TE generation
elements or current collectors, and/or cause chemical and/or
thermal harm to the TE generation elements.
[0084] Those of ordinary skill in the art would understand that the
current collectors 323 can have various configurations and be
formed from various conductive materials including, for example,
metals, alloys, conductive oxides and/or other conductive ceramics.
Furthermore, those of ordinary skill would understand that the TE
generation elements 309 can have various configurations and/or
patterns and be formed from various TE materials, including, for
example, skutterudite-based TE materials, and that the
configuration and material used for the TE generation elements 309
may be chosen as desired based on thermal efficiency (i.e., ZT
value), cost, and other such factors.
[0085] As would also be understood by those of ordinary skill in
the art, various fittings can be used to provide inlets and outlets
for the coolant running through the integrated cooling circuit, as
well as for the electrical power that is generated by the TEG. In
various exemplary embodiments, various fittings may also be used
for feedback and/or control signals. To minimize additional
backpressure that may be created by the fittings, in various
embodiments, fittings can be arranged with a minimum frontal area
as illustrated in FIG. 20.
[0086] As illustrated in FIG. 20, in various exemplary embodiments,
an after-treatment device, such as the after-treatment device 100
in FIG. 8a, may further comprise a housing, such as, for example,
an exhaust gas container 130 that contains the substrate 106.
Accordingly, in various embodiments, when the substrate 106 is
housed within the container 130, TE generation elements 109 (e.g.,
comprising the TEG 105) are disposed entirely within the container
130. Thus, to reach the TEG 105, as shown in FIG. 20, connections
within an inlet fitting 131 and an outlet fitting 132 may breach
the container 130, either radially (as shown in FIG. 20), or at an
inlet 140 and/or outlet 141 of the container 130. The inlet fitting
131 may comprise, for example, a coolant inlet tube 133, a wire 134
for current in and control wiring 135 (if needed), and the outlet
fitting 132 may comprise a coolant outlet tube 136 and a wire 137
for current out. In various embodiments, wires 134, 135 and 137 may
be thermally and electrically insulated using the fittings 131 and
132.
[0087] As those of ordinary skill in the art would understand, for
embodiments with multiple cavities, multiple fittings may be used,
with the possibility of manifold inlets and/or outlets.
[0088] In various additional exemplary embodiments, as shown in
FIG. 21, as an alternative to an enclosed cavity, at least one
slot, which leads to a cavity, may be formed within a substrate and
the TE generation elements and attendant coolant pipes can be
disposed within the cavity and slot. For example, a substrate 906
having a pair of slots 914 that extend from a cavity 915 within the
interior volume of the substrate 906 through the substrate 906 to
open to an exterior of the substrate 906 is illustrated in FIG. 21.
As shown in FIG. 21, each cavity 915 may comprise a volume 70 for
TE generation elements (e.g., comprising a TEG) and a volume 71 for
an integrated cooling circuit. In various embodiments, slots 914
may support ingress/egress of the coolant pipe and the
electrical/control wires from the cavities 915 (see, e.g., FIG.
23).
[0089] FIG. 22 illustrates a cross-sectional view of the embodiment
of FIG. 21. As shown in FIG. 22, the substrate 906 is disposed
within an exhaust gas container 930. TEGs 905 are fitted into the
cavities 915 at the end of each slot 914. The TEGs 905 are
separated from the substrate 906 by an electrically insulating heat
transfer layer 910, and are separated from a central cooling
circuit 908 by an optional electrically insulating layer 911. The
central cooling circuit 908 is defined by a pipe 912 configured to
flow coolant 913 therethrough.
[0090] As with the enclosed cavity embodiments, various fittings
can be used to provide inlets and outlets for the coolant running
through the integrated cooling circuit, as well as for the
electrical power that is generated by the TEG. Furthermore, as
above, in various exemplary embodiments, various fittings may be
used for feedback and/or control signals. To minimize additional
backpressure that may be created by the fittings, in various
embodiments, fittings can also be arranged with a minimum frontal
area as illustrated, for example, in FIG. 23.
[0091] As illustrated in FIG. 23, in various exemplary embodiments,
an after-treatment device may further comprise a housing, such as,
for example, an exhaust gas container 930 that contains the
substrate 906. Accordingly, as before, when the substrate 906 is
housed within the container 930, TEGs 905 are disposed entirely
within the container 930. Thus, to reach the TEGs 909, as shown in
FIG. 23, connections within a fitting 931 may breach the container
930, either radially (as shown in FIG. 23), or at an inlet 940
and/or outlet 941 of the container 930. The fitting 931 may
comprise, for example, a coolant inlet tube 933, a wire 934 for
current in, control wiring 935 (if needed), a coolant outlet tube
936 and a wire 937 for current out. In various embodiments, wires
934, 935 and 937 may be thermally and electrically insulated using
the fitting 931.
[0092] In various additional exemplary embodiments, as illustrated
in FIG. 24, TE generation elements that are disposed within a
cavity within a substrate may be further supplemented by TE
generation elements located around a periphery of the
after-treatment device, outside of the internal volume of the
substrate (e.g., outside of the exhaust gas container). As defined
herein, cavities and slots within a substrate define a volume that
lies within an interior volume of the substrate. Thus,
after-treatment devices in accordance with the present disclosure
comprise at least one TE generation element disposed at least
partially within the interior volume. After-treatment devices in
accordance with the present disclosure may, however, further
comprise at least one thermoelectric generation element disposed
outside of the interior volume (i.e., in combination with TE
generation elements within the interior volume of the substrate).
Such TEGs may be used, for example, as a heater under cold start
conditions to increase a temperature of a catalytic substrate in
order to promote catalysis.
[0093] As illustrated in FIG. 24, an after-treatment device may
comprise a substrate, such as the substrate 406 in FIG. 13, housed
in an exhaust gas container 430. The substrate 406 has a central,
circular cavity 407 comprising multiple rectangular TEGs 405.
Within the cavity 407, an electrically insulating heat transfer
layer 410 separates the TEGs 405 from the body of the substrate
406, while an optional electrically insulating layer 411 separates
the TEGs 405 from an integrated cooling circuit 408 defined by a
rectangular pipe 412 configured to flow a coolant 413 therethrough.
As shown in FIG. 24, the after-treatment device may further
comprise multiple rectangular TEGs 415 around the periphery of the
exhaust gas container 430. Each TEG 415 is in thermal contact with
a respective cooling circuit 418 (i.e., cooling channel) defined by
a rectangular pipe 422 configured to flow coolant 423 therethrough.
Individual electrically insulating heat transfer layers 420
separate each TEG 415 from the body of the exhaust gas container
430, while individual electrically insulating layers 421 separate
each TEG 415 from its respective cooling circuit 418.
[0094] As illustrated in FIG. 25, in various additional
embodiments, an after-treatment device may comprise a substrate 96
having cavities 95 formed within the substrate 96. As shown in FIG.
25, TEGs 99 and attendant coolant pipes 97 can be disposed within
the cavities 95 so that the TEGs 99 are disposed at least partially
within the interior volume 94 of the substrate 96 (and partially
outside the interior volume 94). Within each cavity 95, an
electrically insulating heat transfer layer 91 separates the TEGs
99 from the body of the substrate 96, while an optional
electrically insulating layer 92 separates the TEGs 99 from an
integrated cooling circuit 98 defined by a pipe 97 configured to
flow a coolant therethrough.
[0095] In various additional exemplary embodiments, the disclosure
relates to methods for treating exhaust gas using the
after-treatment devices described herein, such as, for example,
using the after-treatment device 100 of FIG. 8a. More specifically,
a method for dispensing exhaust gas may comprise flowing the
exhaust gas through an interior volume 104 of a substrate 106
having a first end 101, a second end 102, and an outermost lateral
dimension 103 defining the interior volume 104. The method may
further comprise exchanging heat between the flowing exhaust gas
and at least one TE generation element 109 disposed at least
partially within the interior volume 104. As shown in FIG. 8a, in
at least one exemplary embodiment, there may be a plurality of TE
generation elements 109 forming a TEG 105 and the method may
comprise generating electricity via the TEG 105 as a result of the
heat exchange.
[0096] Depending on a particular application, in various
embodiments, the method may further comprise reacting the flowing
exhaust gas with a catalyst incorporated within the substrate 106,
or filtering the flowing exhaust gas within the substrate 106.
[0097] To create a heat sink, in various additional embodiments,
the method may further comprise flowing a coolant through a cooling
circuit 108 in thermal communication with the TE generation element
109.
[0098] To illustrate various principles of the present teachings
and demonstrate how the after-treatment devices disclosed herein
can be effectively utilized to recover waste heat, experiments were
conducted that modeled a TEG disposed within a catalytic converter,
as shown and described in the below example with reference to Table
1 and FIGS. 26-29.
Example
[0099] Modeling results were obtained for power production in a
typical mid-size sedan by a TEG disposed within a catalytic
converter comprising two honeycomb catalytic substrates: a first
honeycomb catalyst substrate with a 4.28 inch diameter, a 4.53 inch
length, and a 1 inch diameter central, round cavity (Sample 1, see,
e.g., FIG. 12), and a second honeycomb catalyst substrate with 4.87
inch diameter, a 4.53 inch length, and a cross-shaped cavity
(Sample 2, see, e.g., FIG. 17). Each substrate had the same length
and frontal area for exhaust gas passage as shown in Table 1.
Furthermore, an inner electrically insulating heat transfer layer
(i.e. an inner mat) was placed between each substrate and cavity,
and an outer electrically insulating layer (i.e., an outer mat) was
placed between each substrate and metal can.
[0100] As shown in Table 1, the model considered three different
substrate web thermal conductivities: k=1, 5, and 15 W/m-K, the
results being shown in FIGS. 26-29.
TABLE-US-00001 TABLE 1 Modeling Assumptions Sample 1 Sample 2 TWC
geometry: 4.28 .times. 4.53 in 4.87 .times. 4.53 in Inner cavity
size: 1 in diameter, circular 3 .times. 3 in cross TE thickness:
0.2 in 0.2 in TE effective conductivity: 2 W/m-K 2 W/m-K Inner mat
thickness: 0.1 in 0.1 in Inner mat conductivity: 5 W/m-K 5 W/m-K
Outer mat thickness 0.1 in 0.1 in Outer mat conductivity 0.1 W/m-K
0.1 W/m-K Substrate conductivity: 1 W/m-K 1 W/m-K 5 W/m-K 5 W/m-K
15 W/m-K 15 W/m-K TWC cell geometry: 600/4 600/4 Coolant
temperature 85.degree. C. 85.degree. C.
[0101] As shown in FIGS. 26 and 27, due to the difference in
surface area for heat transfer between the Samples (i.e., the
surface area for heat transfer from the substrate to the TEG for
Sample 2 was about 382% larger than Sample 1), the total thermal
energy drawn from the TEG was larger for Sample 2 than for Sample
1. As shown in FIG. 28, however, the thermal energy drawn flux,
which was measured by the total thermal energy drawn divided by the
surface area for heat transfer, naturally decreased as the
available surface area increased. Thus, since higher thermal energy
draw results in a lower substrate temperature; the drop (i.e.,
flux) was relatively moderate at about 90% for both samples.
[0102] Accordingly, assuming a conversion efficiency of about 10%,
an electrical power output of about 140 W was obtained for a high
thermal conductivity substrate (i.e., k=15 W/m-K) at a driving
speed of about 80 km/hr (see FIG. 27).
[0103] As shown in FIG. 29 for Sample 2, if the mat thermal
conductivity was low, thermal energy drawn from the substrate was
also sensitive to the inner mat material used (wherein the dotted
line represents the thermal energy drawn with no inner mat). The
impact was relatively high for the condition investigated (i.e.,
thermal energy drawn at 100 km/hr with a thermal conductivity k=5
W/m-K), for example, if the mat conductivity was lower than about 2
W/m-K.
[0104] As used herein, the singular forms "a," "an" and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, reference to a "metal" includes
examples having two or more such "metals" unless the context
clearly indicates otherwise.
[0105] Ranges can be expressed herein as from "about" one
particular value, and/or to "about" another particular value. When
such a range is expressed, examples include from the one particular
value and/or to the other particular value. Similarly, when values
are expressed as approximations, by use of the antecedent "about,"
it will be understood that the particular value forms another
aspect. It will be further understood that the endpoints of each of
the ranges are significant both in relation to the other endpoint,
and independently of the other endpoint.
[0106] Unless otherwise expressly stated, it is in no way intended
that any method set forth herein be construed as requiring that its
steps be performed in a specific order. Accordingly, where a method
claim does not actually recite an order to be followed by its steps
or it is not otherwise specifically stated in the claims or
descriptions that the steps are to be limited to a specific order,
it is no way intended that any particular order be inferred.
[0107] It is also noted that recitations herein refer to a
component of the present invention being "configured" or "adapted
to" function in a particular way. In this respect, such a component
is "configured" or "adapted to" embody a particular property, or
function in a particular manner, where such recitations are
structural recitations as opposed to recitations of intended use.
More specifically, the references herein to the manner in which a
component is "configured" or "adapted to" denotes an existing
physical condition of the component and, as such, is to be taken as
a definite recitation of the structural characteristics of the
component.
[0108] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. Since
modifications combinations, sub-combinations and variations of the
disclosed embodiments incorporating the spirit and substance of the
invention may occur to persons skilled in the art, the invention
should be construed to include everything within the scope of the
appended claims and their equivalents.
* * * * *